JP3243126B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium, that is, an optical disk, and more particularly to a medium having a density exceeding a spatial frequency of a light beam (a frequency defined by a wavelength of a reading light at the time of reproduction and a numerical aperture of an objective lens). The present invention relates to a so-called super-resolution magneto-optical recording medium for recording and reproducing information.

[0002]

2. Description of the Related Art Conventionally, several reading methods have been developed for super-resolution reproduction on an optical disk. In particular,
F for reading information using the temperature distribution of the light spot
AD (Front Aperture Detection) and RAD (Rear Ape
rture Detection) is typical.

FIG. 6 shows a structure of an optical disk for performing a conventional FAD reproduction. FIG. 6A shows a first conventional example (optical disc 1 ′), and FIG. 6B shows a second conventional example (optical disc 1 ″) obtained by improving the optical disc according to the first conventional example.

In FIGS. 6A and 6B, an underlayer 5 is formed.
2, 62 and the protective layers 56, 66 protect the magnetic layer. The reproducing layers 53 and 63 are composed of a Pt / Co laminated film,
The plane of polarization of the read light emitted from the substrate side is rotated according to the direction of the internal magnetization. The intermediate layers 54 and 64 are the reproduction layers 53 and 6
3 and the recording layers 55 and 65 are magnetically exchange-coupled. Further, the intermediate layers 54 and 64 have a low Curie temperature, and the magnetization disappears in a high-temperature region of a light spot irradiated during reproduction. The recording layers 55 and 65 are magnetized in a predetermined direction during recording.

FIG. 7 shows a temperature distribution generated by a light spot when the above-mentioned conventional optical disk is used. FIG.
As shown in FIG.
A light intensity distribution having a maximum point at the center of B occurs. on the other hand,
The maximum point of the temperature distribution generated on the surface of the optical disk occurs at a position slightly backward from the traveling direction of the light spot. F
AD is a reproduction method for performing reproduction by using the first half (low-temperature area A _L ) of the light spot LB having a relatively low temperature in the temperature distribution of the light spot.

When the light spot LB is irradiated, the surface temperatures of the optical disks 1 'and 1 "and the temperatures of the respective magnetic layers rise. In the low temperature region A _L , the intermediate layers 54 and 64 do not reach the Curie temperature, and thus have magnetization. Does not disappear, and the intermediate layers 54 and 6
4 transmits the exchange coupling force between the reproducing layers 53 and 63 and the recording layers 55 and 65. Therefore, the magnetization directions of the magnetic domains of the recording layers 55 and 65 are changed through the intermediate layers 54 and 64 to the reproduction layers 53 and 6.
3 is transmitted.

However, the temperature of the latter half of the light spot LB (high-temperature region A _H ) is further increased, and in the high-temperature region A _H , the magnetization of the intermediate layers 54 and 64 exceeds the Curie temperature and disappears. When the magnetization disappears, the exchange coupling force also disappears. For example, the composition of the intermediate layers 54 and 64 is changed to Dy ₂₂ (Fe ₉₀ C
o ₁₀ ) _{Assuming 78} [at%], the temperature at which the magnetization disappears is about 1
It will be 50 ° C. Therefore, the directions of magnetization of the recording layers 55 and 65 are not transmitted to the reproducing layers 53 and 63, and the directions of magnetization of the reproducing layers 53 and 63 are directed to the reproducing magnetic field applied from the outside. Sokuchi, it becomes impossible to reproduce information from the high-temperature region A _H, it will act as a mask region.

When the light spot passes through and becomes low temperature again, as the magnetization of the intermediate layers 54 and 64 is generated, the recording layers 55 and 6 are generated.
The direction of magnetization of No. 5 is transmitted to the reproducing layers 53 and 63 to prepare for the next reproduction.

FIG. 8 shows the hysteresis characteristic of the Kerr rotation angle of the first conventional optical disc 1 '. Usually, the requirements for transferring the magnetization of the recording layer to the reproducing layer, the exchange coupling force therebetween H _Wpb, when the coercive force of the reproducing layer and _{H Cpb, H Wpb> H Cpb} ... (1) the relationship is Necessary and practically sufficient C / N (carrier-
To obtain a to-noise ratio) is, H _Wpb -H _Cpb 1
[KOe] or more is required. However, in the first conventional example, FIG. 8 shows the reproduction layer (Pt / C
o _Wpb -H
_Cpb is only about 0.7 [kOe], and a sufficient C / N cannot be obtained.

[0010] As the reason, as can be seen from the two Fig. 8, it can be said that the exchange coupling force H _W with fundamentally reproducing layer and the intermediate layer is weak. That is, the exchange coupling force HW is affected by the film formation conditions and composition, but in the case of the optical disk 1 'of the first conventional example, the composition of the intermediate layer, TbFe, is the Pt / C of the reproducing layer.
o The exchange coupling force with the laminated film does not work sufficiently. To cope with this, it is necessary to adjust the composition of the intermediate layer.

In order to improve this, the composition of the intermediate layer is adjusted in a second conventional example. FIG. 9 shows the hysteresis characteristic of the Kerr rotation angle of the optical disc 1 "of the second conventional example. As shown in FIG.
In the hysteresis characteristics of the multilayer film), H _Wpb -H _Cpb
Is about 2.6 [kOe], which indicates that the exchange coupling force between the recording layer and the intermediate layer is sufficient.

[0012]

However, in the optical disk according to the second conventional example, although the exchange coupling force between the intermediate layer and the reproducing layer is sufficient, when the C / N is actually measured, it is not sufficient. Characteristics have not been obtained.

The above C / N is, for example, 34 [d in the first conventional optical disc under the following conditions.
B], a value of 25 [dB] is measured in the second conventional optical disc.

C / N characteristic measurement conditions Wavelength λ 680 [nm] Numerical aperture NA 0.55 Linear velocity 4.24 [m / s] Recording information frequency 5.3 [MHz] Mark length 0.4 [μm] Writing Laser output P _w 5.5 [mW] Recording magnetic field strength H _w 500 [Oe] Reading laser output P _r 2.0 [mW] Reproduction magnetic field strength H _r 600 [Oe] Originally ideal for optical discs 40 [dB] as reproduction characteristics
These conventional optical discs do not have sufficient characteristics because it is said that a certain degree of C / N is required.

The cause will be discussed below. Observation of FIG. 9 shows that two hysteresis loops overlap in the second conventional example. FIG. 9 shows a hysteresis loop of the reproducing layer. Another hysteresis loop overlaps the hysteresis loop of the reproducing layer. This characteristic is the hysteresis characteristic of the intermediate layer. This indicates that the intermediate layer is more strongly exchange-coupled to the reproducing layer than to the recording layer. This is because when the magnetization of the intermediate layer once disappears in the high-temperature region and becomes low-temperature again, and the magnetization occurs, the direction of the magnetization is uniformly aligned not with the direction of the magnetization of the recording layer but with the direction of the reproducing magnetic field of the reproducing layer. Means that As a result, even in the low-temperature region, the magnetization direction of the recording layer is not sufficiently transmitted to the reproducing layer, so that a suitable C / N cannot be obtained.

An object of the present invention is to provide a magneto-optical recording medium exhibiting good C / N characteristics.

[0017]

In order to achieve the above object, the exchange coupling force between the intermediate layer and the recording layer is increased while maintaining the exchange coupling force between the reproducing layer and the intermediate layer at a constant level. It is necessary to make the latter relatively larger.

In FIG. 9, the coercive force of the reproducing layer is H _Cpb ,
_Assuming that the exchange coupling force is H _Wpb , the coercive force of the intermediate layer is H _Cmd , and the exchange coupling force is H _Wmd , the magneto-optical recording medium has a sufficient C / N _ratio.
In order to obtain, it is necessary to have a relationship of _{H Wpb + H Cpb <H Wmd} -H Cmd ... (2). In order to make the optical disk of the second conventional example have the relationship of equation (2), the exchange coupling force H _Wmd between the intermediate layer and the recording layer may be increased.

In general, the exchange coupling force acting between two magnetic layers in contact with each other is an interaction of a common ferromagnetic element in both compositions. In the second conventional example, when the compositions of the intermediate layer and the recording layer are compared, only the transition metals iron (Fe) and cobalt (Co) have strong interaction, and there is no strong interaction from rare earth. Therefore, it is presumed that in the optical disk of the second conventional example, a sufficient exchange coupling force did not work despite the fact that the intermediate layer and the recording layer were ferrimagnetic materials made of the same rare earth-transition metal alloy. You.

Therefore, if a magnetic layer having both rare earth elements is inserted between two layers having different rare earth elements, the magnetic exchange coupling force between the two layers having different compositions increases. I can expect that.

Therefore, the magneto-optical recording medium of the present invention is
Metals mainly composed of platinum (Pt) and cobalt (Co)
Structure of platinum or metal (Pt)
And an alloy structure mainly composed of cobalt (Co)
Magneto-optical recording medium having magnetic layer positioned on irradiation side of read light
A rare body containing dysprosium (Dy) as a main component
Earth and iron (Fe) and cobalt (Co) as main components
The first Curie temperature T mainly containing an alloy with a transition metal
_C1And a first magnetic layer having terbium (Tb).
Rare earth and iron (Fe) and cobalt (Co)
A second key mainly composed of an alloy of a transition metal and a main component;
Curie temperature T_C2A second magnetic layer having
Earth containing both terbium (Ty) and terbium (Tb)
And iron (Fe) and cobalt (Co) as main components
A third Curie temperature T mainly containing an alloy of a transition metal and
_C3And is interposed between the first magnetic layer and the second magnetic layer.
A third magnetic layer, and the Curie temperature of the first magnetic layer.
Degree T_C1, Curie temperature T of the second magnetic layer_C2, The third magnetism
Curie temperature T of the layer_C3And regeneration temperature T_pbBetween T _C1<
T_pb<T_C2And T_C1≤T_C3≤T_C2Have the relationship

[0022]

The present invention will be described with reference to the reproduction principle diagram of FIG. FIG. 1 shows the directions of magnetization of the respective magnetic layers by arrows. As shown in FIG. 1, the reproducing layer 4 functions as a state change layer. The reproducing layer 4 corresponds to a magnetic layer located on the irradiation side of the reading light, and the intermediate layer 5 corresponds to a first magnetic layer. The recording layer 7 corresponds to a second magnetic layer, and the intermediate auxiliary layer 6 corresponds to a third magnetic layer. The intermediate auxiliary layer 6 (third magnetic layer) is the same ferrimagnetic material as the intermediate layer 5 (first magnetic layer) and the recording layer 7 (second magnetic layer). Since the intermediate auxiliary layer 6 contains dysprosium (Dy) and terbium (Tb), the intermediate layer 5 and the recording layer 7 are magnetically exchange-coupled, and the magnetization of the recording layer 7 is transferred to the intermediate layer 5.

In each magnetic layer, a downward arrow indicates a magnetic domain holding recording information '0', and an upward arrow indicates a magnetic domain holding recording information '1'. The recording information is recorded in the recording layer 7 as a magnetization direction by a strong external magnetic field exceeding its own coercive force.

During reproduction, a reproduction magnetic field Hpb is applied from the outside. In a region where the light spot LB is not irradiated onto the optical disc, the magnetization of the recording layer 7 is changed by the strong exchange coupling force due to the action of the intermediate auxiliary layer 6 according to the present invention.
Is transferred to

When the optical disk 1 rotates and the light spot LB is irradiated on the optical disk 1, the surface temperature of the disk becomes
It rises as shown by the temperature rise curve in FIG. The first half of the light spot LB is a low temperature area A _L where the temperature rise is low. In this region, since the exchange coupling force is not cut off since the Curie temperature T _C2 of the intermediate layer 5 is lower than that, the magnetization of the recording layer 7 is
Is transferred to

[0026] In addition, the second half of the light spot LB is in the high temperature area A _H. At this time, the temperature of the intermediate layer 5 becomes _{equal to} or higher than the Curie temperature T _C2 , and the magnetization disappears. When the magnetization disappears, the exchange coupling force that defines the direction of the magnetization of the reproducing layer 4 disappears. The direction of magnetization of the reproducing layer 4 always faces the direction of the reproducing magnetic field _Hpb . The state of magnetization in the low temperature region A _L is “0” as recorded information, which is equivalent to a state where information cannot be actually read, that is, a mask has been made.

Further, the light spot LB passes.
And the temperature of the intermediate layer 5 is the Curie temperature T _C2It becomes below. This
The direction of magnetization of the intermediate layer 5 at the time of
As a result, the direction of the magnetization of the recording layer 7 is transferred as it is. During ~
When a magnetic domain is generated in the intermediate layer 5, the exchange between the intermediate layer 5 and the reproducing layer 4 is performed.
Due to the coupling force, the magnetization of the reproducing layer 4 changes the direction of the magnetization of the recording layer 7.
Will be the same as

As described above, according to the magneto-optical recording medium of the present invention, since the intermediate auxiliary layer 6 is interposed, the reproducing layer 4
Since the exchange coupling force between the recording layer 7 and the intermediate layer 5 is further increased while maintaining the exchange coupling force between the recording layer 7 and the intermediate layer 5 sufficiently large, the transfer of the magnetization from the recording layer 7 to the reproducing layer 4 can be favorably performed. . Therefore, in the reproduction based on the FAD method, the reproduction apparatus can separate information with a high degree of separation, and C / N is improved.

[0029]

Next, a preferred embodiment of the present invention will be described with reference to the drawings. (I) First Embodiment FIG. 2 shows an optical disc according to a first embodiment of the present invention.

As shown in FIG. 2, the optical disk 1 of the first embodiment has a substrate 2 for protecting the surface and transmitting light, an underlayer 3 for protecting the magnetic film and transmitting light, and a light spot for reproducing light. A reproducing layer 4 that rotates the plane of polarization of read light in accordance with the direction of internal magnetization by irradiation, and an intermediate layer 5 that transmits exchange coupling force between the reproducing layer 4 and the recording layer 7 and loses magnetization in a high-temperature region of a light spot. An intermediate auxiliary layer 6 which is a feature of the present invention for transmitting a magnetic exchange coupling force between the intermediate layer 5 and the recording layer 7; and a recording layer 7 which exhibits a high coercive force and is magnetized by a recording magnetic field during recording.
And a protective film 8 for protecting the recording layer 7.

Next, the composition of each film will be described. The underlayer 3 and the protective layer 8 function to protect films below the reproducing layer 4. The base film 3 also has a function of improving the Kerr rotation angle by the generation layer 4. The properties of the underlayer 3 and the protective layer 8 do not affect optically.
It is necessary to have a dense composition that is transparent and does not transmit moisture or the like. As the composition of the underlayer 3 and the protective layer 8, AlN, Ta ₂ O ₅ or the like can be used in addition to SiN of FIG. The film must have a thickness (for example, about 20 [nm]) or more that can resist aging and oxidation, and a thickness that does not affect the heat conduction characteristics and the light transmission characteristics. (For example, about 100 [nm]).

The reproducing layer 4 functions as a state change layer that causes a so-called Kerr rotation that rotates the plane of polarization of the light beam. The properties of the film of the reproducing layer 4 are perpendicular magnetization upon irradiation with a light beam, exhibit magneto-optical properties typified by the Kerr effect or the Faraday effect, and indicate the rotation angle of the polarization plane rotation corresponding to the direction of the internal magnetization. Need to change. As the composition of the reproducing layer 4, in addition to the platinum-cobalt laminated film (Pt / Co) of FIG. 1, a Pt—Co alloy, GdFeCo
It is also possible to use a ferrimagnetic material having the following composition. The thickness of the reproducing layer 4 is such that the reflectivity of the film itself is about 40% in order to utilize the Kerr effect (for example, 8
[Nm]) or more, and the film has a magnetic property such that the magnetic property of the film can hold a perpendicular magnetization film (for example, about 30 [nm]).
The following is preferred.

The intermediate layer 5 has a function of cutting the exchange coupling force between the reproducing layer 4 and the recording layer 6 in a mask region (high-temperature region A _H ) higher than the reproducing temperature T _pb . As a property of the film of the intermediate layer 5, in the low temperature region of the light spot, the film retains perpendicular magnetization and transmits exchange coupling force, reaches the Curie point in the high temperature region of the light spot, and eliminates magnetic domains. Therefore, the Curie temperature of the intermediate layer 5 should be lower than or equal to the temperature (reproduction temperature T _pb : for example, 100 to 150 ° C.) near the boundary between the low temperature area _AL and the high temperature area A _H of the light spot shown in FIG. Required for _TC2 . As a composition of the intermediate layer 5, an alloy composed of a rare earth mainly composed of Dy or the like and a transition metal mainly composed of FeCo or the like is preferable. When the intermediate layer 5 reaches the Curie point, the reproducing layer 4 and the recording layer 7
Thickness sufficient to break the exchange coupling force with
m] or more, and is effective when the magnetic domain is transferred from the recording layer 7 to the reproducing layer 4 and has a thickness (for example, about 30 [nm]) or less that does not lower the recording sensitivity. Is preferred.

The recording layer 7 is magnetized by an external magnetic field during recording. The properties of the film of the recording layer 7 need to be such that its magnetic domains are not affected by the magnetization possessed by the reproducing layer 4 and that the magnetization does not disappear even at the maximum temperature of the light spot. The composition of the recording layer 7 is preferably an alloy composed of a rare earth mainly composed of Tb or the like and a transition metal mainly composed of FeCo or the like. For example, in addition to the composition of TbFeCo in FIG. 1, GdTbFeCo, GdDyFeCo , NdDy
FeCo or the like is used. The film thickness of the recording layer 7 is a thickness (for example, about 30 [nm] or more) necessary for allowing magnetic domains to exist stably regardless of the direction of magnetization of the reproducing layer, and does not lower the recording sensitivity. Thickness (eg, 100
[Nm] or less).

The above-mentioned reproducing layer 4, intermediate layer 5, and recording layer 7
The composition of the alloy is important. Assuming that the Curie temperature of the reproducing layer 4 is T _C0 , the Curie temperature of the intermediate layer 5 is T _C1 , and the Curie temperature of the recording layer 7 is T _C2 , there is a relationship of T _C1 <T _C2 <T _C0 (3).

Now, the intermediate auxiliary film 6 of the present invention comprises the intermediate layer 5
And the recording layer 7. The intermediate auxiliary layer 6 has a magnetic exchange coupling force between the intermediate layer 5 having a low exchange coupling force and the recording layer 7 and efficiently transfers the magnetization of the recording layer 7 to the intermediate layer 5 and the reproducing layer 4. Provided. The properties of the intermediate auxiliary layer 6 require that a good exchange coupling force acts between the intermediate layer 5 and the recording layer 7. In order to have this property, _assuming that the boundary temperature (reproduction temperature T _pb ) between the high temperature area A _H and the low temperature area A _L of the light spot LB and the Curie temperature of the intermediate auxiliary layer 6 is T _C3 , the Curie temperature of the intermediate layer 5 is It is required that the following relationship be established between the temperature T _C1 and the Curie temperature T _C2 of the recording layer: T _C1 <T _pb <T _C2 and T _C1 ≦ T _C3 ≦ T _C2 .

The composition of the intermediate auxiliary layer 6 needs to include both the components of the intermediate layer 5 and the components of the recording layer 7 in order to transmit the exchange coupling force. That is, in the composition of the intermediate layer 5 and the recording layer 7 in this embodiment, T
The alloy must be made of bDyFeCo.

The thickness of the intermediate auxiliary layer 6 is set to a thickness sufficient to transmit the exchange coupling force between the intermediate layer and the recording layer, and is set to the smallest thickness (for example, 3 nm) that can be produced in manufacturing.
) Or more, but not more than a thickness that does not adversely affect the recording sensitivity (for example, about 30 [nm]).

Under the above conditions, specific compositions and film thicknesses are shown in Table 1 within a range satisfying the equations (3) and (4).

[0040]

[Table 1] In FIG. 2, (Tb ₅₀ Dy ₅₀ ) ₁₉ (Fe ₉₀ Co ₁₀ ) ₈₁ [at%] (5) is listed as a composition showing preferable characteristics of the intermediate auxiliary layer of the first embodiment. is there.

The numerical values in the composition formula represent the atomic ratio of the two alloys and are called atomic percent. For example, the indication that A _n B _m [at%], a n + m = 100, this equation is that this material is a composition by the A atoms and m% of B atoms number in n% of the total atoms means.

FIG. 4 shows the hysteresis characteristic of the Kerr rotation angle of the first embodiment. FIG. 4 shows a hysteresis loop formed by the reproducing layer 4 and a hysteresis loop formed by the intermediate layer 5.

As shown in FIG. 4, the hysteresis loop of the reproducing layer 4 is completely separated from the hysteresis loop of the intermediate layer 5. As described above, according to the first embodiment, the exchange coupling force between the intermediate layer 5 and the recording layer 7 is increased by the action of the intermediate auxiliary layer 6 having the composition of the formula (5), and
Transfer of magnetization to the substrate can be performed satisfactorily. Further, since the intermediate layer 5 of the present embodiment has a good exchange coupling force with the reproducing layer 4, the disc 1 has a high C / N.

For example, under the measurement conditions described in the prior art, the optical disc 1 of the present embodiment has a C / N of 38 [dB].
And good characteristics close to those of an ideal disk. (Ii) Second Embodiment The second embodiment of the present invention shows another composition example of the intermediate auxiliary layer 6 in the composition of each magnetic layer described in the first embodiment.

FIG. 3 shows a sectional view of the magneto-optical recording medium of the second embodiment. As shown in FIG. 3, the optical disk 11 of the second embodiment uses the magnetic layers having the same composition and thickness conditions as those of the first embodiment except for the composition of the intermediate auxiliary layer 6.

The composition ratio of the intermediate auxiliary layer 6 in the second embodiment is (Tb ₃ Dy ₉₇ ) ₁₉ (Fe ₉₀ Co ₁₀ ) ₈₁ [at%] (6).

FIG. 5 shows the hysteresis characteristic of the Kerr rotation angle of the second embodiment. FIG. 5 shows a hysteresis loop by the reproducing layer 4. In the present embodiment, the hysteresis loop by the intermediate layer 5 is not illustrated because it is largely out of the range of the characteristic diagram of FIG.

As described above, the optical disk 11 of the second embodiment
Indicates a high C / N. For example, under the measurement conditions described in the prior art, the optical disk 11 of the present embodiment exhibits a C / N of 38 [dB] and exhibits good characteristics close to the characteristics of an ideal disk, as in the first embodiment. Other Modifications The above embodiments can be variously modified.

For example, although the present embodiment is performed by the FAD system, the present invention can also be applied to the so-called double mask system using the low, middle and high temperature regions of the light spot. In other words, in an optical disc having two magnetic layers that need to perform magnetic exchange coupling, when it is desired that the optical disc has a predetermined characteristic by increasing the exchange coupling force between the two layers, it is desirable that the two layers be disposed between the two layers. What is necessary is just to interpose the third magnetic layer of the present invention. As a result, the exchange coupling force between the two layers is increased by the operation of the present invention, and an optical disk having desired magnetic characteristics can be produced.

In this embodiment, the Kerr rotation is used as the magneto-optical polarization plane rotation. However, if the thickness of each magnetic layer is adjusted so that light can be transmitted, Faraday using transmitted light can be used. The present invention can also be applied to an optical disk utilizing the effect.

[0051]

According to the present invention, there is provided a magneto-optical recording medium having a reproduction layer of a laminated film or an alloy film of a metal mainly composed of platinum (Pt) and a metal mainly composed of cobalt (Co). Since the third magnetic layer (intermediate auxiliary film) has both the composition of the first magnetic layer (intermediate layer) and the composition of the second magnetic layer (recording layer), the reproducing layer and the first magnetic layer ( The exchange coupling force between the first magnetic layer and the second magnetic layer can be increased even in the composition of the first magnetic layer in which the exchange coupling force with the intermediate layer increases. Then, since the magnetization of the first magnetic layer disappears at the reproduction temperature T _pb or higher, the C / F of the FAD system is high in reproduction.
N.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of reproduction according to the present invention.

FIG. 2 is a sectional view of the magneto-optical recording medium of the first embodiment.

FIG. 3 is a sectional view of a magneto-optical recording medium according to a second embodiment.

FIG. 4 is a diagram illustrating a hysteresis characteristic of a car rotation angle according to the first embodiment.

FIG. 5 is a hysteresis characteristic diagram of the Kerr rotation angle when DyFeCo is used for the intermediate layer of the second embodiment.

6A and 6B are cross-sectional views of a conventional FAD type magneto-optical recording medium, wherein FIG. 6A is a first conventional example (using TbFe for an intermediate layer), and FIG. 6B is a second conventional example (for an intermediate layer). DyFeCo).

FIG. 7 is an explanatory diagram of the principle of reading information by the FAD.

FIG. 8 is a hysteresis characteristic diagram of the Kerr rotation angle of the first conventional example (using TbFe for the intermediate layer).

FIG. 9 shows a second conventional example (using DyFeCo for the intermediate layer).
FIG. 4 is a hysteresis characteristic diagram of the Kerr rotation angle of FIG.

[Explanation of symbols]

1, 11 optical disk 1 ', 1 "conventional optical disk 2, 12 substrate 3, 13 underlayer 4, 14 reproduction layer 5, 15 intermediate layer 6, 16 intermediate auxiliary layer 7, 17 recording layer 8, 18 Protective layer 51, 61 Substrate 52, 62 Underlayer 53, 63 Reproducing layer 54, 64 Intermediate layer 55, 65 Recording layer 56, 66 Protective layer A _L Low-temperature region A _H High temperature region LB ... read spot T _C0 through T _C3 ... Curie temperature T _pb ... regeneration temperature H _Wpb ... exchange coupling force H _Cpb exchange coupling force H _WMD ... middle layer of the reproducing layer ... reproducing layer coercivity H _Cmd ... intermediate layer Coercive force

Claims (1)

(57) [Claims] 1. A readout comprising a laminated structure of a metal mainly composed of platinum (Pt) and a metal mainly composed of cobalt (Co) or an alloy structure mainly composed of platinum (Pt) and cobalt (Co). A magneto-optical recording medium having a magnetic layer positioned on the light irradiation side, comprising: an alloy of a rare earth mainly composed of dysprosium (Dy) and a transition metal mainly composed of iron (Fe) and cobalt (Co). A first magnetic layer having a first Curie temperature T _C1 as a main component, a rare earth element having terbium (Tb) as a main component, and iron (F
e) and a transition metal based on cobalt (Co);
A second magnetic layer having a second Curie temperature T _C2 as a main component, a rare earth element containing both dysprosium (Dy) and terbium (Tb), and iron (Fe) and cobalt (Co) as main components. A third magnetic layer mainly composed of an alloy of a transition metal having the third Curie temperature T _C3 and interposed between the first magnetic layer and the second magnetic layer; has the first Curie temperature T _C1 of the magnetic layer, the Curie temperature T _C2 of the second magnetic layer, the third T _C1 between the Curie temperature T _C3 and the regeneration temperature T _pb of the magnetic layer <T _pb <T _C2 and T _C1 ≦ T _C3 ≦ T _C2 .